1. Field of the Invention
This invention relates to the processing of audio signals generated by musical instruments. In particular, the invention relates to an audio signal processor having its controls and processing functionality being removable from a base audio processing device.
2. Description of Related Art
Many musical instruments today, including keyboards, electronic drums, and electric stringed instruments, generate their audio output via electronic means. In particular, the electric guitar is comprised of a stringed instrument with magnetic pickups utilized to create an electric voltage that represents the audio signal of the instrument. In order for an electric guitar to be heard at a reasonable level, it is connected to an amplifier and loudspeakers.
The tonal properties of an electric guitar are the combined result of the instrument itself, as well as any circuits that exist in its signal path including the amplifier and the loudspeakers used. A musician may select a particular instrument, amplifier, and loudspeakers in order to achieve a specific desired sound. To have further control over the sound, effects processors commonly known as “stomp boxes” can be inserted in the signal path between the electric guitar and the amplifier.
Many hundreds of different effect circuits have been created for guitarists to insert into their signal path. These devices typically are housed in a small metal box with a few control knobs on top and a footswitch for turning the effect off and on. The effect that each different unit may generate is predetermined by the circuitry it contains and the controls that are used to adjust the effect's parameters.
When a musician desires to modify the audio signal in a different way than by the stomp boxes he currently is using, another stomp box may be added to the signal chain or may be used to replace an existing stomp box. The sonic range of a given stomp box is determined when it is designed, and other than through physical modification by the user, that designed sonic range is all that can ever be generated.
In order to achieve a diverse array of well-known or classic types of guitar tones, a guitarist has traditionally been required to use many different guitars, amplifiers, and effects, including stomp boxes. With regards to the effects, digital signal processing (DSP) techniques have been developed that provide the user with a wider range of tone than previously available with analog effect circuitry. Although multiple devices may still be required for achieving specific sonic results, the available sounds on each effect unit can include digital emulations of many traditionally analog effects. But in these digitally-based systems, their functionality is still limited to the range of sounds designed into the device at the time of manufacture.
Most recently, some DSP-based effects have provided a means for updating their firmware via a computer interface such as Universal Serial Bus (USB). In this manner, the range of sound available to the musician can be modified via computer software, allowing the effect unit to be updated with new capabilities in the future. However, these developments do not provide a convenient method of changing an effect unit's capabilities without a computer.